Issues in Cervical Vestibular-Evoked Myogenic Potentials

Issues in Cervical Vestibular-Evoked Myogenic Potentials

Blakley and Wong (2015) evaluated 48 normal patients without hearing loss and without vestibular complaints, all of whom underwent cervical vestibular-evoked myogenic potential (cVEMP) testing. The authors note that cVEMP is used to assess the sacular (and inferior vestibular nerve) response to loud sounds through measurement of sternocleidomastoid (SCM) activity. Blakley and Wong report that cVEMP testing is well tolerated by patients, creates less vertigo than other tests, is easy to perform, and may help differentiate central from peripheral problems.

Of note, the Food and Drug Administration (FDA) has not approved cVEMP in the United States for clinical use (and FDA approval is required for the issuance of a CPT code). Fink (2015) reported that “VEMP testing is not yet FDA-approved and at least some insurance companies consider VEMP testing experimental and investigational. Some clinicians are having luck billing VEMP testing as an unspecified code.” She states that “…the primary application of VEMP is to rule out superior semicircular canal dehiscence (SSCD) syndrome. Patients with SSCD usually have a lower-than-normal threshold for the VEMP response. Recent research suggests that cVEMP amplitudes in response to sound are superior to cVEMP thresholds in the diagnosis of SSCD (Zuniga et al, 2013).”

Blakley and Wong report that for their normal population of test subjects, when tested at 100 dBHL, the response rate was 98 percent, which they admit is higher than most reports. Further, they state “the finding that normal subjects are reported as having no response is disconcerting.” Additionally, they report that the cVEMP parameter with the most evidence-based clinical application is the threshold, and indeed, it is threshold that gives “insight into the presence of semi-circular canal dehiscence.” They conclude their normal cVEMP values fall between 70 and 90 dBHL, thresholds should be reported and of note “the clinical importance of other parameters is unknown at this time.”